living in cities are breathing unhealthy air.

Some cities, especially those in developing nations have it particularly bad, with city

officials going to extreme measures to protect residents from respiratory diseases.

So what are the world’s most polluted cities?

Well, ranking cities by their level of pollution is difficult because scientists study air

quality in different ways.

Some score air quality based on the number of particles that are less than or equal to

2 and a half micrometers in diameter, which are produced from all types of combustion

and are small enough to get into your lungs or blood tissue.

Others place more emphasis on particles as large as 10 micrometers in diameter, like

dust and mold.

When ranked according to these larger particles, the most polluted city is Onitsha, Nigeria.

Experts say Onitsha’s pollution is a product of its rapid growth and industrialization.

The city’s population has doubled to more than one million people in the last few years,

leaving its existing infrastructure inadequate and outdated.

As a result, Onitsha has some of the worst traffic in Nigeria, lacks any proper waste

incineration plants and has little to no regulations on its factories, hospitals, metal industries

and other carbon emitters.

When it comes to those smaller particles, the most polluted air is actually in the eastern

Iranian city of Zabol.

Zabol’s pollution problem is somewhat unique, as the city is not a population or industrial

hub.

Instead, its excess air particles are actually a product of continuous dust storms.

Every summer, temperatures in Zabol exceed 104 degrees, and the city is struck with what

locals call, ‘120 days of wind’.

In the early 2000s, the region’s primary wetland dried up, creating another major source

of dust.

Hundreds of residents have since evacuated because of the resulting pollution, and many

who have stayed have been diagnosed with pollution related diseases, like tuberculosis.

In 2015, the air became so dirty that city officials were forced to distribute free face

masks.

But one city that consistently tops the charts is Delhi, India.

According to the World Health Organization, Delhi has the worst air quality of any other

major city in the world, with particle levels twice as high as China’s infamously polluted

Beijing.

Most of Delhi’s air pollution is a product of vehicle emissions, as the city’s enormous

population of nearly 25 million people contributes to heavy traffic.

The effects of Delhi’s pollution are devastating and extremely widespread.

Adults are known to suffer from headaches, sore throats and reduced lung capacity, and

studies suggest that nearly half of all Delhi's children have irreversible lung damage.

Delhi’s air quality becomes measurably worse in the winter, as wind carries in dust from

neighboring regions.

This, combined with other factors, brought the city’s smog levels to new highs in November

of 2016, forcing its people into a full-blown state of emergency.

Schools were closed down, sports games were canceled and residents were encouraged to

stay indoors.

Delhi’s chief minister has taken steps to address the problem, but nothing has been

successful yet in curbing pollution.

To be certain, air pollution is not limited to industrial cities in developing nations.

It’s a global problem, with most of the world’s urban populations already breathing

in hazardous airborne particles on a daily basis.

What’s more, many cities don’t even measure their air quality.

This is only the tip of the iceberg; the real statistics likely paint a much bleaker picture.

There are activists around the world fighting to protect the environment and wildlife.

Seeker Stories filmed with a group of women in South Africa that are fighting off poachers

more effectively than drones or thermal imaging — and they don’t use any weapons.

Black Mamba anti-poaching unit was first founded in 2013, snaring dropped 97 percent in the

first year in this region.

The first 13 months of operation we didn't lose a single rhino throughout the reserve.

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